This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: Request for code review - (ZEE patch : Redundant Zero extension elimination)
- From: Paolo Bonzini <bonzini at gnu dot org>
- To: Diego Novillo <dnovillo at google dot com>
- Cc: Sriraman Tallam <tmsriram at google dot com>, Ian Lance Taylor <iant at google dot com>, Richard Guenther <richard dot guenther at gmail dot com>, rth at redhat dot com, Jie Zhang <jie dot zhang at analog dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Jan Hubicka <jh at suse dot cz>, Uros Bizjak <ubizjak at gmail dot com>
- Date: Fri, 7 May 2010 18:58:28 +0200
- Subject: Re: Request for code review - (ZEE patch : Redundant Zero extension elimination)
- References: <4B4E1F14.7020508@gmail.com> <863b0cbf1001131155t74432d2ela10e2aead1a46195@mail.gmail.com> <4B551B60.3040806@analog.com> <n2q863b0cbf1004301106i2ef3146ci5ef79d2979b29373@mail.gmail.com> <o2q84fc9c001004301114g8457b1csaf062058c9ef5b22@mail.gmail.com> <mcr8w84ojss.fsf@dhcp-172-17-9-151.mtv.corp.google.com> <r2yf865508f1005010030zc7b54ea4h34056d5bd413eaf1@mail.gmail.com> <AANLkTimKF7br-0IkdpMHIteDMAcOf5uhcLjOuAL4QSab@mail.gmail.com> <4BE44197.20101@google.com>
On Fri, May 7, 2010 at 18:36, Diego Novillo <dnovillo@google.com> wrote:
> On 5/3/10 18:56 , Sriraman Tallam wrote:
>
>> +
>> +shr $0x5, %edx
>> +mov %edx, %edx --> Useless zero-extend.
>> +
>> +How to turn on ?
>> +----------------
>> +-fzee -O2
>> +
>> +*/
>
> Please indent this whole comment two spaces.
I think you meant three?
>> +fzee
>> +Common Report Var(flag_zee) Init(0)
>> +Eliminate redundant zero extensions on targets that supports implicit extensions.
>
> s/supports/support/
>
> What happens if the user specifies -fzee on a target that does not
> support implicit extensions?
The pass will simply not find any optimization opportunity.
Paolo